Effects of thermal resistance to fly ash-based lightweight geopolymer

Abstract

Geopolymers are inorganic polymeric materials and cementations materials that replace the Ordinary Portland Cement. This study aimed to determine the effect of thermal resistance of fly ash based lightweight geopolymer and to investigate the physical, mechanical and microstructure properties of lightweight geopolymer at different thermal resistance. Considering the fire endurance assessment of geopolymers, the evolution of geopolymer during thermal exposure is of interest. This paper presents a comparative study of the characteristic of unfoamed (control sample) and lightweight geopolymers after exposure to elevated temperatures which is 200 °C, 400 °C, 600 °C and 800 °C. Lightweight geopolymers were prepared by adding foaming agent which is polyoxyethylene alkyether sulphate with geopolymer paste. Fly ash, alkaline activator and foam were mixed to produce a homogeneous mixture, which was placed into a cube 50 mm x 50 mm x 50 mm mould and cured at 80 °C for 24 hours. The compressive strength, density, chemical composition, microstructure and functional group analyses were studied. Unfoamed geopolymer exhibit higher compressive strength at 47.04 MPa compared to the highest strength of lightweight geopolymer which is 33.26 MPa at 200 °C. However, the lightweight geopolymer produced low density in range 1200 kg/m3 to 1500 kg/m3 compared to the density of unfoamed is 1813.79 kg/m3.